1. Technical Field
The invention relates to blowers of the type comprising a tubular sleeve for guiding the air flow provided with flow-straightening blades carrying a central unit including an electric motor whose shaft carries a propeller located in front of the blades.
2. Prior art
Blowers of the above type are already known. To reduce the costs of such a blower, the manufacturing techniques as economical as possible are used. In particular, for the high through-put industrial blowers, such as those used in mines, the sleeve, the straightening blades and the propeller are produced by casting. However these economical manufacturing techniques have a drawback. The parts produced have a wide size variation. Consequently, considerable clearances must be provided between movable parts. The large clearances and the centering defects cause turbulences which reduce the efficiency and which in addition notably increase the noise.
Compressors and blowers designed for uses for which the obtaining of a high efficiency is of prime importance are also known. In such rotary machines, high efficiency is obtained at a price of a cost not corresponding at all with that of an industrial blower, by machining the major part of the surfaces defining the flow.